This invention relates to rotating machines.
Rotating machines typically include a stationary stator assembly and a rotor assembly that rotates within the stator assembly. The rotor assembly, which is typically cylindrical in shape, includes rotor coils that, during operation, are magnetically linked with armature coils incorporated into the stator assembly. During operation, the stator assembly generates a rotating magnetic field, resulting in the rotation of the rotor assembly. Or, if the rotor assembly is driven by an external machine, the rotating field assembly generates voltages and currents in the stationary stator assembly. As the rotor assembly rotates, it is subjected to radial centrifugal forces that may result in radial distortion of the rotor assembly.
According to an aspect of this invention, a rotor assembly includes a substantially cylindrical support structure having at least one first region, and at least one second region. The rotor assembly further includes at least one rotor coil positioned within each first region of the substantially cylindrical support structure, with each rotor coil including a pair of distal end portions and a convex center portion, wherein the average mechanical density of the convex center portion is substantially equal to the average mechanical density of the distal end portions. Further, the average mechanical density of the first region is substantially equal to the average mechanical density of the second region.
One or more of the following features may be included. One or more of the rotor coils includes a mandrel positioned within an interior region of the rotor coil. The mandrel may occupy a portion of the interior region of the rotor coil and is constructed of a material (e.g., stainless steel, copper, aluminum, phenolic, etc.) having a mechanical density that is greater than the average mechanical density of the first and second regions. The mandrel may occupy the interior region of the rotor coil and is constructed of a material (e.g., stainless steel, copper, aluminum, phenolic, etc.) having a mechanical density that is substantially equal to the average mechanical density of the first and second regions.
The mandrel includes a pair of distal end portions spaced by a pair of convex center portions. The periphery of the distal end portions of the mandrel may be defined by a first radius and the periphery of the convex center portions of the mandrel may be defined by a second radius, such that the second radius is larger than the first radius. Alternatively, the mandrel may be elliptical in shape.
One or more of the second regions may include a member that occupies a portion of the second region and has a mechanical density that is greater than the average mechanical density of the first and second regions. Alternatively, one or more of the second regions may include a member that occupies the second region and has a mechanical density that is substantially equal to the average mechanical density of the first and second regions. These members may be constructed of stainless steel, copper, aluminum, phenolic, etc.
The rotor coils (e.g., racetrack-type or saddle-type coils) may be superconducting coils and include one or more high temperature superconducting windings. These rotor coils, which may or may not be cryogenically cooled, generate a magnetic flux path within the rotor assembly during operation. The substantially cylindrical support structure may define an internal volume that houses a magnetic material having high saturation flux density, which is positioned within at least a portion of the flux path and decreases the overall reluctance of the flux path generated by the rotor coils. This magnetic material within the internal volume may or may not be cryogenically cooled. The conductors within the rotor coil may be wound such that the lines of magnetic flux produced by the rotor coil proximate the convex center portions of the mandrel are essentially radially aligned toward an axial center of the rotor assembly.
The saddle-type coil may be configured such that the lines of magnetic flux produced by the saddle-type coil are perpendicular with a surface of the substantially cylindrical support structure and radially aligned toward an axial centerline of the rotor assembly.
One or more advantages can be provided from the above aspects of the invention. The use of a convex or elliptical mandrel results in rotor coils that have consistent mechanical densities. Further, by matching the average mechanical density of the mandrel to that of the rotor coil, rotor performance can be enhanced. Additional enhancement can be obtained by matching the density of the filler material to that of the rotor coil/mandrel combination. By matching the density of the various components of the rotor assembly, the high speed operation of the rotor can be enhanced, as radial distortion due to centrifugal forces is reduced. Additionally, the use of a magnetic core within the cylindrical support structure of the rotor can enhance magnetic performance by reducing reluctance.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.